1. Field of the Invention
The present invention relates to a high-speed spindle unit for machine tools for machining workpieces.
2. Discussion of Related Art
Modern high-speed spindles are driven with speeds up to several ten thousand rpm, which is, of course, only possible with fully functional and highly precise bearings. The precision bearings used for the spindle of such high-speed spindle units are, however, highly susceptible to pressure or shock loads acting on the tool and spindle body. These loads are, in particular, transmitted to the housing via the front roller bearing. This holds true for impact and shock loads acting on the clamped tool or on the tool spindle, or both. These loads are caused by a collision with a machine part or the workpiece during shifting movements of the workpiece or the spindle unit, or both, while no machining operation is carried out.
Further, extremely high loads may occur during a machining operation, for example, in case of an excessive feeding movement, an erroneously selected cutting tool, or a change of the material structure of the workpiece. In both cases of stress the impact-like shock loads or peak loads may damage the high-precision roller bearings, and thus, affect the true running properties, which are particularly critical. This may lead to a possibly permanent damage of the components involved, which will inevitably require an exchange of the spindle unit.